A light CP-odd Higgs boson and the muon anomalous magnetic moment

We amalgamate the many experimental limits on the ab (b) over bar coupling of a light CP-odd Higgs boson, a, including model-dependence coming from the ratio of the at (t) over bar to the ab (b) over bar coupling. We then employ these limits to analyze the extent to which a light a can make a significant contribution to the discrepancy, Delta a(mu), between the experimentally observed a(mu), and that predicted by the standard model. In a model-independent framework and in the context of a general two-Higgs-doublet model this is a significant possibility. In contrast, the minimal supersymmetric model is too strongly constrained (after combining experimental and theoretical input) to allow a CP-odd-a explanation of Delta a(mu). The next-to-minimal supersymmetric model allows more freedom and the light a of the model could explain the full Delta a(mu) if 9.2 GeV < m(a) < 12 GeV, or contribute substantially for larger m(a), if tan beta is large.